Thailand has asked Interpol for help in tracking down the man they believe planted a bomb in Bangkok that killed 20 people, sending the international police organisation an image of the suspected bomber.

The military government was initially reluctant in asking for outside help in the investigation of the blast at a famous shrine on Monday evening that killed 20 people and wounded scores.

There has been no claim of responsibility and police have not determined a motive for the worst ever bomb attack in Thailand.